Vacuum cleaner is a consumer appliance for performing cleaning with a fan motor for generating suction power, a suction nozzle for sucking in air of a surface to be cleaned, and a dust collector for separating and collecting dirt from the air sucked in.
The vacuum cleaner may be divided by shape into a canister type, upright type, handy type, robot cleaner type, etc.
In the common upright type vacuum cleaner, a wheel is equipped for the suction unit having the suction nozzle, and a handle unit having the fan motor, the dust collector, and a handle is rotationally combined with the suction unit. Accordingly, the suction unit remains upright in ordinary times, but during cleaning, the user performs cleaning by tilting the handle unit.
While tilting the handle unit, the user is burdened with the weight of the handle unit. In other words, extra burden from torque due to gravity applied to the handle unit is placed on the user in addition to an operating force to operate the handle unit.
Meanwhile, a vacuum cleaner employing a gravity compensation mechanism that uses elasticity of an elastic member to relieve the burden on the user by compensating the torque due to gravity is known. An example of this vacuum cleaner is disclosed in Korean Patent Publication No. 2001-0035934.
The vacuum cleaner disclosed in the publication includes a main cleaning body, a brush assembly rotationally combined with the main cleaning body, a shaft formed in the main cleaning body, and a torsion spring to support elasticity of the main cleaning body with one end fixed on the shaft and the other end fixed on the brush assembly, and compensates torque due to gravity applied to the main cleaning body with elastic force of the torsion spring.
However, with the gravity compensation mechanism disclosed in the publication, although the torque due to gravity applied to the main cleaning body may be compensated to some extent, it is difficult to compensate the torque as precisely as even the main cleaning body becomes in no weight state.
The reason is that since the magnitude of the torque due to gravity and the magnitude of the elastic torque of the torsion spring change independently according to an angle at which the main cleaning body is tilted, it is not easy or impossible to design a standard of the torsion spring to correspond the magnitude of the torque due to gravity with the magnitude of the elastic torque of the torsion spring at every angle.